This invention relates to a suspension system and, more particularly, a suspension system having partial etched areas to limit and control the adhesive coverage between a flex circuit interconnect and the suspension.
Today the demand for high performance, low cost and nonvolatile information storage systems is ever increasing. There are a variety of information storage systems with varying degrees of development and commercialization, including magnetic tape drives, magnetic hard disc drives, magnetic floppy disc drives, magnito-optic (MO) disc drives, phasechange optic disc drives, semiconductor flash memory, magnetic random access memory (RAM), and holographic optical storage. To date, magnetic information storage technology, (hard disc, floppy disc and tape drives) is most widely used.
Direct access storage devices (DASD), or disc drives, store information on concentric tracks of an erodable magnetic recording disc. A magnetic head or transducer element is moved from track to track to record and read the desired information. Typically, the magnetic head is positioned on an air bearing slider which flies above the surface of the disc as the disc rotates. A suspension assembly connects the slider to a rotary or linear actuator. The suspension provides support for the slider.
The suspension must be flexible and provide a biased force in the vertical direction. This is necessary to provide a compensating force to the lifting force of the air bearing in order to keep the slider at a correct height above the disc. Also, the vertical flexibility is needed to allow the slider to be loaded and unloaded away from the disc. Further, the suspension must be rigid in the lateral direction. This is needed to prevent the head from moving from side to side, which will result in the head reading the wrong track. Further yet, the suspension must have a frequency response that satisfies the requirements of a disc drive system. A desirable frequency response consists of resonances high in frequency and low in gain. The present suspension systems typically use flanged load beams which exhibit undesirable low frequency bending, and sway modes. This is especially true where the flange height of the suspension is relatively small.
Systems employing dampening methods have been in use for quite some time. Several such dampening methods are disclosed in Pal et al., U.S. Pat. No. 4,760,478; Erpelding et al., U.S. Pat. No. 5,781,379, and Gifford et al., U.S. Pat. No. 5,483,397. However, the problem with all of these methods is that the use of adhesive is not confined to a predetermined area and may not aid in dampening of a first torsion resonance mode.
Resonance is inherent in mechanical structures. The impact of resonance must be minimized in disc drives. A resonance mode may be caused by the high speed rotation of the discs, actuation of the suspension using the coil motor, and air disturbances, created by high spinning disc speeds, against the suspension. Whenever these resonance modes become excited, they cause large gains or high offsets of the slider thereby causing a loss of a signal. A head-gimbal assembly (HGA) first torsion mode mechanical resonance results in significant drive level yield loss. HGA roll stiffness variation is a significant contribution to fly height sigmas in disc drives, which in turn directly impacts the drive yield. Reduction in roll stiffness variation is critical to reduction of fly height sigmas. Both of these issues have been attributed to an excessive bonding area between the flex circuit interconnect and the suspension in the HGA.
HGA""s of the prior art are designed without adhesive control features. An adhesive used to bond the interconnect to the suspension is dispensed in an etched area of the suspension until it is full. Because there are no adhesive control features, in many cases the adhesive overflows into unwanted areas such as in a xe2x80x9cforward glue dotxe2x80x9d area thereby bonding the flex circuit interconnect in this unwanted area. Further, the adhesive being used usually is a high viscosity material. Thus, bonding the flex circuit interconnect in the forward glue dot area results in increased roll stiffness of the HGA which directly impacts its fly height performance in the drive.
Present suspension systems have a problem in achieving low enough pitch and roll stiffness for the air bearing flying height tolerances while at the same time achieving high enough lateral stiffness to prevent relative motion between the slider and the supporting end of the suspension. Some sliders may even attempt to compensate for irregularities in manufacture and operation by pitching and/or rolling slightly to maintain the air bearing.
However, the current suspension design and the lack of adhesive control allow for very poor control of the flex circuit interconnect/suspension bonding area. This results in the adhesive being dispensed on the suspension in the xe2x80x9cforward glue dotxe2x80x9d area of the suspension resulting in a higher roll stiffness. Also, the first torsion gains are increased due to the increased amount of interconnect to suspension bonding which in turn reduces the vibrations of the unbonded portions of the interconnect. These vibrations are effective in dampening the suspension vibrations in the first torsion resonance mode.
It can be seen that there is a need to reduce the first torsion gains in a suspension system.
It can also be seen that there is a need to limit and control the adhesive coverage between the flex circuit interconnect and the suspension.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention generally discloses a suspension system and, more particularly, a suspension system having an adhesive control feature.
The present invention solves the above-described problems by limiting and controlling the bonding area between the flex circuit interconnect and the suspension thereby reducing gains in the first torsion resonance mode and reducing roll stiffness.
A method in accordance with the principles of the present invention provides a bonding surface located on a first side of the suspension. An etched area surrounding the bonding surface, wherein the etched area is recessed with reference to the bonding surface.
The bonding area between the flex circuit interconnect and the suspension terminates at the etched portion of the suspension. This bonding area terminates because the flex circuit interconnect does not contact the bonding surface of the suspension in the etched areas. These etched areas are generally referred to as adhesive dams.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect is to create a bonding surface having a cross-shaped area and island-shaped area located towards a center area of the suspension. Further, the suspension includes an etched area creating a forward dam located remotely from the bonding area. The suspension also prevents bonding of the flex circuit interconnect to the suspension in a tail and a side region allowing movement between the flex circuit and suspension, wherein the movement dampens a first torsion resonance mode. In addition, adhesive bonding in specific areas may decrease the rigidity of the suspension and roll stiffness of a head-gimbal assembly.